This invention relates generally to flexible packages, and more particularly to flexible packages for particulate products, such as dry pet foods, and which tend to be abrasive.
There are a multitude of laminated materials used to package dry products, such as roasted and ground coffee, active dry yeast, roasted peanuts, etc., under vacuum. The following are some of these laminated materials (where the "/" symbol represents an adhesive interface between the adjacent layers and wherein the materials are listed in sequence from the outside of the package to the inside thereof): polyester film/aluminum foil/nylon film/polyethylene film; polyester film/aluminum foil/polyethylene film; polyester film/polypropylene film/aluminum foil/polyethylene film; polyester film/nylon film/polyethylene film; polyester film/aluminum foil/polyester film/polyethylene film; polypropylene film/aluminum foil/polyethylene film; nylon film/aluminum foil/polyethylene film; and others. Some of the above vacuum package constructions are further protected with a layer of Kraft paper or Kraft paper laminated with another material, such as polyester film or aluminum foil. The paper construction is either wrapped around the finished vacuum package, combined with the vacuum material on the packaging machine prior to filling, vacuumizing and sealing, or produced as a "Double Wall" construction, such as described in my U.S. Pat. No. 4,727,706.
Moreover, various types of flexible packages for holding dry cat, dog, or other pet foods, are commercially available. For example, such packages may be formed of a heavy paper, like Kraft paper, and having an inner lining of a plastic or wax to provide a moisture barrier and to prevent any oil or grease in the pet food from staining the paper.
In U.S. Pat. No. 5,491,011 (Pezzoli et al.) there is disclosed a flexible sheet material for forming packages for dry pet foods which have an odoriferous component. The structure of that sheet material from the inside of the package to the outside comprises linear low density polyethylene, high density polyethylene, linear low density polyethylene, a barrier resin such as ethylene vinyl alcohol copolymer, and low density polyethylene.
Unfortunately dry pet foods frequently exhibit sharp edges or particles (e.g., in some cases the pet food may include particles of bone), and tend to abrade the flexible material making up the package. Thus, it is necessary that the material forming the packaging for such particulate material pet foods be resistant to abrasion or abuse. Moreover, it is desirable that the material forming the package be capable of holding the contents of the package under vacuum, be moisture and odor impervious, and be resistant to grease or oil.
Heretofore, flexible packaging of various types of plastic films and/or foils which have been commercially available for holding free flowing products under vacuum have not proven to be generally suitable for sharp edged dry pet foods. Thus, a need exists for a flexible package which can hold such materials under vacuum, yet which exhibits substantially reduced package leakage due to abuse as compared to other typical flexible materials.